A Clojure function for atoms that I'm currently missing

bigswap.clj

(defn bigswap!
  "`swap!` into an atom *and* return a custom value produced in the atomic function.

  `atom` is the atom.
  `f` is a function of two arguments: the first is a function `atom-set` that 'sets' the atom to the given value.
  The second is the current value in the atom.

  In essence, `bigswap!` returns the value of `f` while setting the value of the atom to the value set by `atom-set`, if applicable."
  [atom f]
  (let [return-val (volatile! nil)]
    (swap!
     atom
     (fn [a]
       (let [res (volatile! a)
             atom-set (partial vreset! res)
             ret (f atom-set a)]
         (vreset! return-val ret)
         @res)))
    @return-val))